1. Field of the Invention
The present invention relates to a data correcting apparatus that corrects print image data representing a print image to be printed by a printing system, and to a computer-readable data correcting program storage medium.
2. Description of the Related Art
In the field of printing, a print image is conventionally formed in the following manner. An image is first edited with the use of a personal computer or the like, and a film original plate is produced based on the edited image. Based on the film original plate, a printing plate is formed, and is mounted to a printing machine. Ink is then applied to the printing plate, and the applied ink is transferred onto a printing paper sheet. In recent years, a CTP (Computer To Plate) that burns an image directly into a printing plate is incorporated into a printing machine to form a digital printing machine that automatically carries out complicated plate producing procedures that used to require a highly-skilled worker. In this trend, there is an increasing demand for a printing machine for fewer lots and more variety to produce various kinds of printed materials in fewer lots than in a case of a conventional printing machine.
The series of procedures to be carried out to perform printing on paper sheets involve the troublesome process of printing hundreds of copies at one time, and therefore, are time-consuming and costly. To counter this problem, a proof image showing an image to be printed is formed by a printer or the like that is easier to handle than a printing machine prior to performing actual printing. The image to be printed is checked in advance through the proof image. In recent years, soft proof is conducted by displaying a proof image on a calibrated monitor, so as to prevent a waste of paper and readily check an image to be printed during each process in a printing operation.
However, a proof image displayed on a monitor conventionally used only to grasp the pattern in an image to be printed or a rough entire image. The colors in a print image and the finish of the print image including the ink thickness or the like are checked by actually printing the image with a printing machine. Since the preferred ink thickness varies depending on print media such as newspaper, advertisement, poster, or magazine, a user manually opens and closes the ink key of a printing machine to adjust the printing density until desired print colors are obtained, while operating the printing machine to repeatedly perform test printing when a print image is formed. Therefore, a certain skill is required to adjust ink printing density, and a large amount of paper waste is generated in the end. The amount of paper waste generated before the final ink printing density is determined is almost the same, regardless of the number of copies to be printed. The paper waste generation rate becomes higher, if the number of copies to be printed becomes smaller. Therefore, in a digital printing machine for fewer lots and more variety, the period of time required to determine the final ink printing density should be shortened to achieve high speed, and generation of paper waste should be reduced to lower costs.
To counter those problems, Japanese Patent Application Publication No. 2001-347645 discloses a technique for displaying a predicted image on a monitor. The predicted image is formed by predicting a print image based on the opening of the ink key for adjusting the ink printing density and the pixel values of image data. Japanese Patent Application Publication No. 2004-106523 discloses a technique for setting a target color that is a sample color printed by a reference printing machine already subjected to a color adjustment, and automatically adjusting the ink printing density so that each image printed by a printing machine to be adjusted has a similar color to the target color. By the technique disclosed in Japanese Patent Application Publication No. 2001-347645, the colors in each image to be printed can be roughly checked prior to printing, and accordingly, the processing time required to determine the final ink printing density can be shortened. By the technique disclosed in Japanese Patent Application Publication No. 2004-106523, the ink printing density can be automatically adjusted so as to reproduce the sample color printed by the reference printing machine.
However, even if the ink printing density is adjusted to obtain a print color similar to the target color by the techniques disclosed in Japanese Patent Application Publication Nos. 2001-347645 and 2004-106523, there might be a request to make a quick change in the print color, as a result of a check made by a client on a predicted image displayed on a monitor or test print image. Particularly, a request for color correction on each of the image components in a print image is often made. In such a case, the print colors are adjusted by manually changing the ink printing density, and test printing is repeated until a print image satisfying the client's request is obtained. Therefore, a large amount of paper waste is generated, and it is still difficult to adjust the color of each image component in a print image to a desired print color through the adjustment of the ink printing density.